Tape carrier package with dummy bending part and liquid crystal display employing the same

ABSTRACT

A tape carrier package has dummy bending parts that are capable of reducing a brightness difference of a screen. In the tape carrier package, a pad part is connected to a liquid crystal panel. A base film is mounted with an integrated circuit chip for applying a signal to the liquid crystal panel. A dummy bending part is formed by removing the base film between the pad part and the integrated circuit chip to distribute a stress applied to the liquid crystal panel according to a thermal expansion of the pad part.

[0001] This application claims the benefit of Korean Patent ApplicationNo. P2000-17026, filed on Mar. 31, 2000, which is hereby incorporated byreference for all purposes as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to an apparatus for mounting an integratedcircuit on a liquid crystal display, and more particularly to a tapecarrier package with a dummy bending part that is capable of reducing adifference in brightness in a screen. Also, the present invention isdirected to a liquid crystal display that is capable of reducing adifference in brightness, using said tape carrier package.

[0004] 2. Description of the Related Art

[0005] Generally, a liquid crystal display with an active matrix drivingsystem uses thin film transistors (TFTs) as switching devices to displaya natural moving picture. Since such a liquid crystal display can bemade into a smaller-size device than the Brown tube, it is commerciallyavailable for a monitor such as a portable television or a lap-toppersonal computer, etc.

[0006] The active matrix liquid crystal display displays a picturecorresponding to video signals, such as television signals, on a pixel(or picture element) matrix having pixels arranged at each intersectionbetween gate lines and data lines. Each pixel includes a liquid crystalcell for controlling a transmitted light quantity in accordance with avoltage level of a data signal from a data line. The TFT is installed atan intersection between the gate line and the data line to switch a datasignal to be transferred to the liquid crystal cell in response to ascanning signal (i.e., a gate pulse) from the gate line.

[0007] Such a liquid crystal display requires a number of drivingintegrated circuits, each hereinafter referred to as a “D-IC”, connectedto the data lines and the gate lines to apply data signals and scanningsignals to the data lines and the gate lines, respectively. The D-ICsare installed between the printed circuit board (PCB) and the liquidcrystal panel to apply the data signals and the scanning signals to thedata lines and the gate lines of the liquid crystal panel in response toa control signal applied from the PCB. A tape automated bonding (TAB)system has generally been used as a mounting method of the D-ICs that iscapable of widening an effective area of the panel and has a relativelysimple mounting process.

[0008] The TAB method may be divided into a bending type as shown inFIG. 1A, and a flat type as shown in FIG. 1B. The bending-type TABsystem as shown in FIG. 1A has been used for a mounting of source andgate drivers of a monitor or a notebook computer. In the bending-typeTAB system, a PCB 6 is folded to the rear side of a liquid crystal panel2 by bending a tape carrier package (TCP) 10 mounted with a D-IC 8 andconnected between a lower glass substrate 3 of the liquid crystal panel2 and the PCB 6. As shown in FIG. 2 and FIG. 3, an adhesive 25 is coatedon a base film 24 of the TCP 10, and a lead part 26 is adhered thereon.The lead part 26 made from copper (Cu) is connected to pins of the D-IC8. On the lead 26 is coated a solder resistor 27 responsible forproviding an insulator. At the upper end and the lower end of the basefilm 24, an input pad part 21 and an output pad part 22 extending fromeach lead of the lead part 26 are provided. The input pad part 21 isconnected to an output signal wiring of the PCB while the output padpart 22 is connected to the gate line or the data line formed on a lowerglass substrate 3. Bending parts 10 a and 10 b are provided between theinput pad part 21 and the D-IC 8 and between the output pad part 22 andthe D-IC 8, respectively. The base film 24 is removed from the bendingparts 10 a and 10 b. The TCP 10 is easily bent with the aid of thesebending parts 10 a and 10 b.

[0009] The flat-type TAB system as shown in FIG. 1B is mainly used tomount gate drivers of a 10.4″ or 12.1″ small-size notebook computer ormonitor. In the flat-type TAB system, a TCP 12 mounted with a D-IC 8 andconnected between a lower glass substrate 3 of a liquid crystal panel 3and a PCB 6 is arranged in parallel to the liquid crystal panel 2. Thus,since the TCP 12 connected between the liquid crystal panel 2 and thePCB 6 is not bent, no bending part is formed.

[0010] However, the conventional TAB system has a problem in that abrightness difference is generated between an area where the TCP 10 or12 is adhered onto the liquid crystal panel 2 and an area where the TCP10 or 12 is not adhered onto the liquid crystal panel 2. Morespecifically, as shown in FIG. 4, the TCPs 10 c to 10 j are adhered tothe edge of the lower glass substrate 3 at a desired spacing, having ananisotropic conductive film (ACF) therebetween under a high temperatureand high pressure atmosphere. At this time, the TCPs 10 c to 10 j areexpanded by heat and then contracted while the heat applied thereto islowered to a normal temperature after their adhesion. A stress isapplied to the lower glass substrate 3 by such TCPs 10 c to 10 j. As aresult, since the lower glass substrate 3 is deformed into a periodicalland/groove shape as shown in FIG. 5, a cell gap between an upper glasssubstrate (not shown) and the lower glass substrate 3 has a periodicalthickness difference. When an experiment using the gray patterns of ‘7’and ‘3’ was made with respect to two samples of a 12.1″ liquid crystalpanel as shown in FIG. 4 having SVGA resolution (i.e., 800×600) and abrightness of 300 nit, a brightness difference is periodicallygenerated. As a result of this experiment, a brightness differencebetween the adhesive areas a, c, e, g, i and k and the non-adhesiveareas b, d, f, h and i of the TCPs 10 c to 10 j having a difference inthe cell gap is indicated in the following Table 1, and in FIGS. 6 and7. As a brightness measuring device, a ‘PR800’ model opticalmeasuring-set is used for sensing a brightness level in accordance witha received light amount. TABLE 1 Measuring Sample Point a b c d e f g hi j k Sample 1 7-Gray 0.577 0.74 0.679 0.879 0.818 0.956 0.801 0.9590.829 0.957 0.794 3-Gray 0.44 0.538 0.491 0.642 0.577 0.703 0.584 0.7070.604 0.712 0.596 Sample 2 7-Gray 1.628 2.075 1.892 2.293 1.974 2.1652.165 2.563 2.217 2.587 2.132 3-Gray 1.925 1.233 1.089 1.369 1.129 1.4641.258 1.564 1.291 1.549 1.245

[0011] As seen from Table 1, a brightness difference is generatedbetween the adhesive areas a, c, e, g, i and k and the non-adhesiveareas b, d, f, h and l of the TCPs 10 c to 10 j. In two samples, averagebrightness differences in the 7 gray pattern and the 3 gray pattern have0.2691 and 0.1957, respectively. Since a stress applied to the lowerglass substrate 3 by the TCPs 10 a to 10 h becomes larger as the TCPs 10c to 10 j become longer or thicker, a brightness difference between theadhesive areas a, c, e, g, i and k and the non-adhesive areas b, d, f, hand l of the TCPs 10 c to 10 j becomes larger. Therefore, a strategycapable of reducing a brightness difference caused by the TCPs 10 c to10 j is required to improve a display quality of the liquid crystaldisplay.

[0012]FIG. 6 is a characteristic diagram of a brightness level detectedfrom the liquid crystal panel shown in FIG. 4 with respect to a 7-graypattern;

[0013]FIG. 7 is a characteristic diagram of a brightness level detectedfrom the liquid crystal panel shown in FIG. 4 with respect to a 3-graypattern;

SUMMARY OF THE INVENTION

[0014] Accordingly, it is an object of the present invention to providea tape carrier package with a dummy bending part that is capable ofreducing a brightness difference of the screen.

[0015] A further object of the present invention is to provide a liquidcrystal display that is adaptive for reducing a brightness difference ofthe screen.

[0016] In order to achieve these and other objects of the invention, atape carrier package according to one aspect of the present inventionincludes a pad part connected to a liquid crystal panel; a base filmmounted with an integrated circuit chip for applying a signal to theliquid crystal panel; and a dummy bending part for distributing a stressapplied to the liquid crystal panel according to a thermal expansion ofthe pad part by removing the base film between the pad part and theintegrated circuit chip.

[0017] A tape carrier package according another aspect of the presentinvention includes a base film mounted with an integrated circuit chipfor applying a signal to a liquid crystal panel; a pad part extendingfrom the integrated circuit chip to be connected to the liquid crystalpanel; at least one bending part in which the base film at a portionwhere the tape carrier package is folded is removed; and at least onedummy bending part, in which a desired base film at a portion where thetape carrier package is not folded is removed, for reducing a thermalexpansion force and a thermal contraction force of the base filmparallel to the longitudinal direction of the integrated circuit chip.

[0018] A liquid crystal display device according to still another aspectof the present invention includes a liquid crystal panel; a tape carrierpackage connected to the liquid crystal panel; a base film mounted withan integrated circuit chip for applying a signal to the liquid crystalpanel; at least one bending part in which the base film at a portionwhere the tape carrier package is folded is removed; a dummy bendingpart, in which the base film is removed in a direction perpendicular toterminals of the pad part, for reducing a thermal expansion force and athermal contraction force generated at the time of thermal-pressing thepad onto the liquid crystal panel; and a printed circuit board connectedto an input pad part of the tape carrier package.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] These and other objects of the invention will be apparent fromthe following detailed description of the embodiments of the presentinvention with reference to the accompanying drawings, in which:

[0020]FIG. 1A is a sectional view showing the conventional bending-typetape automated bonding (TAB) system;

[0021]FIG. 1B is a sectional view showing the conventional flat-typetape automated bonding (TAB) system;

[0022]FIG. 2 is a plan view showing the structure of the tape carrierpackage in FIG. 1A;

[0023]FIG. 3 is a sectional view of the tape carrier package taken alonga line A-A′ in FIG. 2;

[0024]FIG. 4 is a plan view showing the structure of a liquid crystalpanel to which tape carrier packages used as a sample for brightnessmeasurement are attached;

[0025]FIG. 5 depicts a deformation of the lower substrate glasssubstrate caused by the tape carrier package;

[0026]FIG. 6 is a characteristic diagram of a brightness level detectedfrom the liquid crystal panel shown in FIG. 4 with respect to a 7-graypattern;

[0027]FIG. 7 is a characteristic diagram of a brightness level detectedfrom the liquid crystal panel shown in FIG. 4 with respect to a 3-graypattern;

[0028]FIG. 8 is a plan view showing the structure of a tape carrierpackage according to a first embodiment of the present invention;

[0029]FIG. 9 is a sectional view of the tape carrier package taken alongline B-B′ in FIG. 8;

[0030]FIG. 10 is a plan view showing the structure of a tape carrierpackage according to a second embodiment of the present invention;

[0031]FIG. 11 is a sectional view of the tape carrier package takenalong line C-C′ in FIG. 10;

[0032]FIG. 12 is a plan view showing the structure of a tape carrierpackage according to a third embodiment of the present invention; and

[0033]FIG. 13 is a plan view showing the structure of a tape carrierpackage according to a fourth embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0034] Referring to FIG. 8 and FIG. 9, there is shown a tape carrierpackage (TCP) according to a first embodiment of the present invention,which is applicable to the bending-type TAB system. The TCP includes aD-IC 38 mounted on a base film 44, a first bending part 30 a providedbetween an input pad part 41 and the D-IC 38, and a second bending part30 b and a dummy bending part 30 c provided between an output pad part42 and the D-IC 38 in parallel. The D-IC 38 plays a role to applyscanning signals, or data, to gate lines or data lines of a liquidcrystal panel 2. Output pins of the D-IC 38 are connected to a lead part46 adhered onto the base film 44 by means of an adhesive 45.

[0035] The lead part 46 is coated with a solder resistor 47 responsiblefor providing an insulator. At the input pad part 41 are formed padsextending from the lead part 46 to be connected to an output signalwiring of a PCB 6. Between the input pad part 41 and the D-IC 38 isprovided the first bending part 30 a in which the base film 44 isremoved. The TCP between the PCB 6 and the D-IC 38 is easily bent by thefirst bending part 30 a. At the output pad part 42 are provided padsextending from the lead part 46 to be connected to pads formed at theedge of the lower glass substrate 3. Between the output pad part 42 andthe D-IC 38 is provided the second bending part 30 b and the dummybending part 30 c in which the base film 44 are removed. The TCP betweenthe liquid crystal panel 2 and the D-IC 38 is easily bent by the secondbending part 30 b. The dummy bending part 30 c reduces the TCP area towhich heat is applied at the time of adhering the TCP to the lower glasssubstrate. Accordingly, since the amount of thermal expansion of the TCPis reduced, the stress applied to the lower glass substrate 3 by the TCPis distributed and thus reduced.

[0036] Referring to FIG. 10 and FIG. 11, there is shown a tape carrierpackage (TCP) according to a second embodiment of the present invention,which is applicable to the bending-type TAB system. The TCP includes aD-IC 38 mounted on a base film 54, a first bending part 50 a providedbetween an input pad part 51 and the D-IC 38, and a second bending part50 b, a first dummy bending part 50 c and a second dummy bending part 50d provided between an output pad part 52 and the D-IC 38 in parallel toeach other. At the input pad part 51 are formed pads extending from thelead part 56 to be connected to an output signal wiring of a PCB 6.Between the input pad part 51 and the D-IC 38 is provided the firstbending part 50 a in which the base film 54 is removed. The TCP betweenthe PCB 6 and the D-IC 38 is easily bent with the aid of the firstbending part 50 a. At the output pad part 52 are provided pads extendingfrom the lead part 56 to be connected to pads formed at the edge of thelower glass substrate 3. Between the output pad part 52 and the D-IC 38are provided the second bending part 50 b, the first dummy bending part50 c and the second dummy bending part 50 d in which each of the basefilm 54 is removed. The TCP between the liquid crystal panel 2 and theD-IC 38 is easily bent by the second bending part 50 b. The first andsecond dummy bending parts 50 c and 50 d play a role to distribute andreduce a stress applied to the lower glass substrate 3 by the TCP. A TCParea to which heat is applied at the time of adhering the TCP onto thelower glass substrate 3 is reduced more than in the TCP of FIG. 8, withthe aid of the second dummy bending part 50 d.

[0037] Referring to FIG. 12 and FIG. 13, there are shown tape carrierpackages (TCPs) according to other embodiments of the present invention,which are applicable to the flat-type TAB system. Each of the TCPsincludes a D-IC 38 mounted on a base film 54, and at least one of dummybending part 60 a or 60 b and 60 c between an output pad part 62 and theD-IC 38. At the input pad part 61 are formed pads extending from thelead part 56 to be connected to an output signal wiring of a PCB 6. Atthe output pad part 62 are provided pads extending from the lead part 56to be connected to pads formed at the edge of the lower glass substrate3. Between the output pad part 62 and the D-IC 38 are provided one ortwo dummy bending parts 60 a or 60 b and 60 c in which the base film 54is removed. The dummy bending parts 60 a, 60 b and 60 c play a role todistribute and reduce a stress applied to the lower glass substrate 3 bythe TCP.

[0038] As described above, according to the present invention, the basefilm close to the output pads adhered onto the glass substrate of theliquid crystal panel is removed, so that a stress applied to the glasssubstrate by the TCP is distributed and thus reduced. As a result, theTCP with dummy bending parts according to the present invention canreduce a brightness difference of the screen. Furthermore, according tothe present invention, the TCP having the dummy bending parts isadhered, so that a stress applied to the glass substrate as well as acell gap difference between the adhesive area and the non-adhesive areaof the TCP is reduced to that extent. Accordingly, the liquid crystaldisplay according to the present invention maintains the cell gapconstantly at the adhesive area and the non-adhesive area of the TCP, sothat it is capable of reducing a brightness difference of the screen.

[0039] Although the present invention has been explained by theembodiments shown in the drawings described above, it should beunderstood to the ordinary skilled person in the art that the inventionis not limited to the embodiments, but rather that various changes ormodifications thereof are possible without departing from the spirit ofthe invention. Accordingly, the scope of the invention shall bedetermined only by the appended claims and their equivalents.

What is claimed is:
 1. A liquid crystal display device, comprising: aliquid crystal panel; a printed circuit board; and a tape carrierpackage connected to the liquid crystal panel and the printed circuitboard, the tape carrier package comprising, a base film mounted with anintegrated circuit chip for applying a signal to the liquid crystalpanel, an output pad part extending from the integrated circuit chip andhaving terminals connected to the liquid crystal panel, a dummy bendingpart in which a portion of the base film is removed in a directionperpendicular to the terminals of the output pad part for reducing athermal expansion force and a thermal contraction force generated whenthermal-pressing the output pad part onto the liquid crystal panel, afirst bending part in which a second portion of the base film existingat a bent position between the dummy bending part and the integratedcircuit chip is removed, and an input pad part extending from theintegrated circuit chip and having terminals connected to the printedcircuit board.
 2. The liquid crystal display device of claim 1 , whereinthe tape carrier package further comprises a second bending part inwhich a third portion of the base film existing at a bent positionbetween the input pad part and the integrated circuit chip is removed.3. The liquid crystal display panel of claim 2 , wherein the tapecarrier package further comprises a second dummy bending part in which afourth portion of the base film is removed in a direction perpendicularto the terminals of the output pad part.
 4. The liquid crystal displaydevice of claim 1 , wherein the tape carrier package further comprises asecond dummy bending part in which a third portion of the base film isremoved in a direction perpendicular to the terminals of the output padpart.
 5. A tape carrier package, comprising: a pad part for connectionto a liquid crystal panel; a base film mounted with an integratedcircuit chip for applying a signal to the liquid crystal panel; and adummy bending part for distributing a stress applied to the liquidcrystal panel according to a thermal expansion of the pad part byremoving a portion of the base film between the pad part and theintegrated circuit chip.
 6. The tape carrier package according to claim5 , further comprising a first bending part in which a second portion ofthe base film is removed at a bent position between the dummy bendingpart and the integrated circuit chip.
 7. The tape carrier packageaccording to claim 6 , further comprising a second pad part forconnection to a printed circuit board.
 8. The tape carrier packageaccording to claim 7 , further comprising a second bending part in whicha third portion of the base film is removed at a bent position betweenthe second pad and the integrated circuit chip.
 9. The tape carrierpackage according to claim 5 , further comprising a second pad part forconnection to a printed circuit board.
 10. The tape carrier packageaccording to claim 5 , further comprising a second dummy bending part inwhich a second portion of the base film is removed.
 11. The tape carrierpackage according to claim 10 , further comprising a first bending partin which a third portion of the base film is removed at a bent positionbetween the dummy bending part and the integrated circuit chip.
 12. Thetape carrier package according to claim 11 , further comprising a secondpad part for connection to a printed circuit board.
 13. The tape carrierpackage according to claim 12 , further comprising a second bending partin which a fourth portion of the base film is removed at a bent positionbetween the second pad and the integrated circuit chip.
 14. A tapecarrier package, comprising: a base film mounted with an integratedcircuit chip for applying a signal to a liquid crystal panel; a pad partextending from the integrated circuit chip to be connected to the liquidcrystal panel; at least one bending part in which a portion of the basefilm is removed at an area where the tape carrier package is folded; andat least one dummy bending part, in which a second portion of the basefilm is removed at a portion where the tape carrier package is notfolded, thereby reducing a thermal expansion force and a thermalcontraction force of the base film parallel to a longitudinal directionof the integrated circuit chip.
 15. The tape carrier package accordingto claim 14 , wherein said dummy bending part is positioned on the padpart.